Tuesday, August 22, 2017

Azure Managed Disks: How Azure VMs Are Moving To PaaS

When implementing Azure VMs one is using Azure as an IaaS solution offering. At least this is how Microsoft introduced Azure VMs back in 2012. However, things are moving with a fast pace in IT and in todays cloud things are moving with lighting speed.

As such it’s time to take a new look at Azure VMs in order to know whether they still adhere to the IaaS cloud delivery model only, or that things have changed a ‘bit’.

Azure VMs as IaaS
Sure, when you opt for the ‘classic’ approach to roll out an Azure based VM, it’s IaaS at its best. You need to provision a Storage Account, perhaps even Diagnostics storage account for monitoring, a Virtual Network and so on. Let’s focus on the Storage Accounts here.

When rolling out Azure VMs in the classic manner you have to think about your Azure subscription limits, since per subscription one is only allowed a certain amount services and resources. For instance per Azure subscription one is ‘only’ allowed 200 Storage Accounts (default) with a maximum of 250 (requires contacting Microsoft Support).

Of course, you could use only ONE Storage Account for all your Azure based VMs. But that approach isn’t going to ‘fly’ since per Azure Storage Account there are limits as well, like 20,000 IOPS per Azure Storage Account. So when you ‘hook up’ too many Azure VMs to the same Azure Storage Account, the available IOPS per Azure VM will drop dramaticly, resulting in under performing VMs.

In an ideal world one would prefer to facilitate one Storage Account per Azure VM. However, when requiring 250+ VMs, this approach isn’t viable. Even when the total amount of Azure VMs stays well below the 250 mark, there are still quite a few reasons why not to use 1:1 (VM:Storage Account) approach.

As a result, deploying an Azure VM requires planning, preparations, guidance and administration afterwards. Without it, sooner or later your company will have serious problems with Azure VM resource allocation and the lot…

Azure VMs as IaaS++
How nice would it be to roll out Azure VMs without  the headache of managing storage accounts? Instead, Azure manages storage for you! In this case you only have to think about the type & size of the disks.

All of the above (and much more) is delivered by Azure Managed Disks.

So now we’re talking about a new kind of Azure VMs. Sure the Azure VMs themselves are still adhering to the IaaS cloud delivery model, BUT a very important component of that same Azure VM (the disks and underlying storage) has become a different ball game all together.

Instead of doing it all yourself, Azure manages it for you. So the disks – when using Azure Managed Disks that is – have become IaaS++ at least, perhaps even more like a PaaS solution? Of course, this ‘statement’ could result in a never ending discussion on semantics. Let’s not go there please.

But no matter how you look at it, Azure VMs with Azure Managed Disks have evolved the cloud IaaS delivery model in that respect to a whole new level.

Azure VMs with Azure Managed Disks are the next level of how Azure can enlighten the regular burden of VM management and administration as a whole. It also brings Azure VMs as IaaS to a new level. One might say IaaS++ or even – the storage management that is when Azure Managed Disks is being used – as a PaaS cloud delivery model.

Should my company use Azure Managed Disks?
Good question! Before you make any decision it’s vital to know what Azure Managed Disks deliver and how their costs are stuctured.

For instance, Azure Managed Disks deliver better high availability out of the box. Simply because these disks are automatically placed in different storage units. So when one storage unit goes down, it won’t affect many VMs but one or a subset instead.

Also with Azure Managed Disks it’s much easier to copy an image across multiple storage accounts and so on.

On top of it all, there are two types of ‘flavors’ (AKA performance tiers) for Azure Managed Disks: Premium (SSD based) and Standard (HDD based).

Also good to know: With Azure Managed Disks you can create 10,000 Azure Managed Disks per subscription, per region and per storage type! For example, you can create up to 10,000 standard managed disks and also 10,000 premium managed disks in a subscription and in a region. As a result you can create thousands of VMs in a single subscription.

As you can see, there is much more to Azure Managed Disks, all of which has to be taken into account when making a decision.

Recommended resources
For a better understanding of this article I recommend to read these resources:

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